The present disclosure relates generally to communication systems, and more particularly, to improving handling of fingers with large delay spread through utility optimization.
Wireless communication networks are widely deployed to provide various communication services such as telephony, video, data, messaging, broadcasts, and so on. Such networks, which are usually multiple access (e.g., multipath) networks, support communications for multiple users by sharing the available network resources. One example of such a network is the UMTS Terrestrial Radio Access Network (UTRAN). The UTRAN is the radio access network (RAN) defined as a part of the Universal Mobile Telecommunications System (UMTS), a third generation (3G) mobile phone technology supported by the 3rd Generation Partnership Project (3GPP). The UMTS, which is the successor to Global System for Mobile Communications (GSM) technologies, currently supports various air interface standards, such as Wideband-Code Division Multiple Access (W-CDMA), Time Division-Code Division Multiple Access (TD-CDMA), and Time Division-Synchronous Code Division Multiple Access (TD-SCDMA). The UMTS also supports enhanced 3G data communications protocols, such as High Speed Packet Access (HSPA), which provides higher data transfer speeds and capacity to associated UMTS networks.
A rake receiver is a radio receiver designed to counter the effects of multipath fading. It does this by using several “sub-receivers” called fingers, that is, several correlators each assigned to a different multipath component. The rake receiver is so named because it reminds the function of a garden rake, each finger collecting symbol energy similar to how tines on a rake collect leaves. Rake receivers are common in a wide variety of CDMA and W-CDMA radio devices such as mobile phones and wireless LAN equipment. Each finger may independently decode a multipath component. Multipath components may be delayed copies of an original transmitted wave traveling through a different path (e.g., transmissions from a repeater may be delayed in comparison to transmissions from an originating base station or Node B), each with a different magnitude and time-of-arrival (also referred to as phase) at the receiver. Since each component contains the original information, if the magnitude and time-of-arrival (phase) of each component is computed at the receiver (through a process called channel estimation), then all the components can be added coherently to improve the information reliability.
Cell delay spread is a metric used in system design. The cell delay spread may be used to determine other system designs, such as transmit power control (TPC), turn-around time distribution between firmware (FW) and hardware (HW), length of sample reading for each block processing group (BPG), and/or the like. However, with the widely deployed repeaters, cell delay spreads greater than the maximum value may be seen. Generally, signals from a repeater may be stronger than those received directly from a base station or Node B.
Therefore, improvements in handling fingers with large delay spreads may be desired.